In vibration actuators, progressive vibration waves (hereafter, called progressive waves) are generated on a driving face of an elastic body using the expansion and contraction of an electromechanical conversion element, elliptic motion is generated at the driving face by these progressive waves, and a relative moving element in pressure-contact with the wave crests of the elliptic movement is driven.
Much consideration has been given to improving the driving efficiency and driving performance of such vibration actuators, and as one example, Patent Document 1 discloses a vibration actuator where the width w in the radial direction of the electrode portion of the piezoelectric body is provided to be wider than the width in the radial direction of the flexural center of the elastic body.
However, in the method disclosed in Patent Document 1, there is the problem that the vibration actuator becomes large.    Patent Document 1: Japanese Unexamined Patent Publication No. 2004-297869.